Extract Blog Thumbnails for Archive Page

models/posts/index.go

@@ -15,8 +15,9 @@ func UpdateIndex(p *Post) error {
 
 // Index caches high level metadata about the blog's contents for fast access.
 type Index struct {
-	Posts     map[int]Post   `json:"posts"`
-	Fragments map[string]int `json:"fragments"`
+	Posts      map[int]Post   `json:"posts"`
+	Fragments  map[string]int `json:"fragments"`
+	Thumbnails map[int]string `json:"thumbnails"`
 }
 
 // GetIndex loads the index, or rebuilds it first if it doesn't exist.
@@ -33,8 +34,9 @@ func GetIndex() (*Index, error) {
 // RebuildIndex builds the index from scratch.
 func RebuildIndex() (*Index, error) {
 	idx := &Index{
-		Posts:     map[int]Post{},
-		Fragments: map[string]int{},
+		Posts:      map[int]Post{},
+		Fragments:  map[string]int{},
+		Thumbnails: map[int]string{},
 	}
 	entries, _ := DB.List("blog/posts")
 	for _, doc := range entries {
@@ -65,6 +67,12 @@ func (idx *Index) Update(p *Post) error {
 		Updated:        p.Updated,
 	}
 	idx.Fragments[p.Fragment] = p.ID
+
+	// Find a thumbnail image if possible.
+	if thumb, ok := p.ExtractThumbnail(); ok {
+		idx.Thumbnails[p.ID] = thumb
+	}
+
 	err := DB.Commit("blog/index", idx)
 	return err
 }

models/posts/posts.go

@@ -18,6 +18,12 @@ var DB *jsondb.DB
 
 var log *golog.Logger
 
+// Regexp used to parse a thumbnail image from a blog post. Looks for the first
+// URI component ending with an image extension.
+var (
+	ThumbnailImageRegexp = regexp.MustCompile(`['"(]([a-zA-Z0-9-_:/?.=&]+\.(?:jpe?g|png|gif))['")]`)
+)
+
 func init() {
 	log = golog.GetLogger("blog")
 }
@@ -191,6 +197,16 @@ func (p *Post) Delete() error {
 	return idx.Delete(p)
 }
 
+// ExtractThumbnail searches and returns a thumbnail image to represent the
+// post. This will be the first image embedded in the post, or nothing.
+func (p *Post) ExtractThumbnail() (string, bool) {
+	result := ThumbnailImageRegexp.FindStringSubmatch(p.Body)
+	if len(result) < 2 {
+		return "", false
+	}
+	return result[1], true
+}
+
 // getNextID gets the next blog post ID.
 func (p *Post) nextID() int {
 	// Highest ID seen so far.

models/posts/thumbnail_test.go

@@ -0,0 +1,63 @@
+package posts_test
+
+import (
+	"testing"
+
+	"github.com/kirsle/blog/models/posts"
+)
+
+func TestThumbnailRegexp(t *testing.T) {
+	type testCase struct {
+		Text       string
+		Expect     string
+		ExpectFail bool
+	}
+
+	var tests = []testCase{
+		{
+			Text:       "Hello world",
+			ExpectFail: true,
+		},
+		{
+			Text: "Some text.\n\n![An image](/static/photos/Image-1.jpg)\n" +
+				"![Another image](/static/photos/Image-2.jpg)",
+			Expect: "/static/photos/Image-1.jpg",
+		},
+		{
+			Text: `<a href="/static/photos/12Abc456.jpg" target="_blank">` +
+				`<img src="/static/photos/34Xyz123.jpg"></a>`,
+			Expect: "/static/photos/12Abc456.jpg",
+		},
+		{
+			Text: `A markdown image: ![With text](/test1.gif) and an HTML ` +
+				`image: <img src="/test2.png">`,
+			Expect: "/test1.gif",
+		},
+		{
+			Text:   `<a href="https://google.com/"><img src="https://example.com/logo.gif?query=string.jpg"></a>`,
+			Expect: "https://example.com/logo.gif?query=string.jpg",
+		},
+	}
+	for _, test := range tests {
+		p := &posts.Post{
+			Body: test.Text,
+		}
+
+		result, ok := p.ExtractThumbnail()
+		if !ok && !test.ExpectFail {
+			t.Errorf("Text: %s\nExpected to fail, but did not!\nGot: %s",
+				test.Text,
+				result,
+			)
+			continue
+		}
+
+		if result != test.Expect {
+			t.Errorf("Text: %s\nExpect: %s\nGot: %s",
+				test.Text,
+				test.Expect,
+				result,
+			)
+		}
+	}
+}

root/blog/archive.gohtml

@@ -3,22 +3,40 @@
 
 <h1>Archive</h1>
 
+{{ $thumbs := .Data.Thumbnails }}
+
 {{ range .Data.Archive }}
-    <h3>{{ .Date.Format "January, 2006" }}</h3>
+    <div class="card mb-4">
+        <div class="card-header">
+            <h3>{{ .Date.Format "January, 2006" }}</h3>
+        </div>
+        <div class="card-body">
 
-    <ul class="list-unstyled">
-    {{ range .Posts }}
-        <li class="list-item">
-            <a href="/{{ .Fragment }}">{{ .Title }}</a>
-            <small class="blog-meta">
-                {{ .Created.Format "Jan 02 2006" }}
-                {{ if ne .Privacy "public" }}
-                    <span class="blog-{{ .Privacy }}">[{{ .Privacy }}]</span>
+            <div class="row">
+                {{ range .Posts }}
+                {{ $thumb := index $thumbs .ID }}
+                <div class="col-12 col-sm-6 col-md-4 col-lg-3 mb-4">
+                    <div class="card bg-secondary"
+                        style="height: auto; min-height: 150px;
+                        {{ if $thumb }}background-image: url({{ $thumb }}); background-size: cover{{ end }}
+                        "
+                        title="Tags: {{ range .Tags }}#{{ . }} {{ end }}">
+                        <span class="p-1" style="background-color: RGBA(255, 255, 255, 0.8)">
+                            <a href="/{{ .Fragment }}">{{ .Title }}</a><br>
+                            <small class="blog-meta">
+                                {{ .Created.Format "Jan 02 2006" }}
+                                {{ if ne .Privacy "public" }}
+                                    <span class="blog-{{ .Privacy }}">[{{ .Privacy }}]</span>
+                                {{ end }}
+                            </small>
+                        </span>
+                    </div>
+                </div>
                 {{ end }}
-            </small>
-        </li>
-    {{ end }}
-    </ul>
+            </div>
+
+        </div>
+    </div>
 {{ end }}
 
 {{ end }}

src/controllers/posts/archive.go

@@ -5,8 +5,8 @@ import (
 	"sort"
 	"time"
 
-	"github.com/kirsle/blog/src/middleware/auth"
 	"github.com/kirsle/blog/models/posts"
+	"github.com/kirsle/blog/src/middleware/auth"
 	"github.com/kirsle/blog/src/render"
 	"github.com/kirsle/blog/src/responses"
 	"github.com/kirsle/blog/src/types"
@@ -54,7 +54,8 @@ func archiveHandler(w http.ResponseWriter, r *http.Request) {
 	}
 
 	v := map[string]interface{}{
-		"Archive": result,
+		"Archive":    result,
+		"Thumbnails": idx.Thumbnails,
 	}
 	render.Template(w, r, "blog/archive", v)
 }